The invention described herein was made in the course of, or under, United States Energy Research and Development Administration Contract No. W-7405-ENG-48 with University of California.
This invention relates to isotope separation processes. More particularly this invention relates to a method of isotope separation by photodissociation of Van der Waal's molecules.
Several processes for isotope separation make use of the isotope shift, that is, a slight shift of the lines in the absorption spectra of elements or molecular species due to the small difference in nuclear mass of the isotopes of the same element contained therein. Changes in nuclear mass can shift electronic, vibrational, and rotational energy levels. When the shift places the absorption line of one isotopic species at a frequency at which the others are transparent, it is possible to excite selectively that species with a source of radiation of sufficiently narrow width.
A common feature of all separation methods based on the isotope shift is the selective excitation of one of the isotopic species by radiation, particularly laser radiation, tuned to a specific absorption line, followed by a physical or chemical process which acts on excited species and separates them from unexcited ones. The method for realizing separation following selective excitation of an atom or molecule may or may not require the absorption of a second photon.
The isotope separation schemes which do not require photon absorption to effect separation of excited species from unexcited ones are sometimes referred to as "one-photon or one quantum step processes", the one photon being used, theoretically, for the selective excitation step. For example, the excited species could spontaneously undergo an irreversible change as in predissociation, preionization, or isomerization. Or a chemical reagent could be used which both reacts with the excited state so rapidly that energy transfer cannot occur and reacts with the ground state so slowly that the reagents can be mixed without reaction. Various isotope separation schemes based on the foregoing concepts are described in C. Bradley Moore, Accounts of Chemical Research 6 323 (1975).
The one-photon processes have the potential for lower laser energy requirements. However, the known onephoton processes generally require photon energies which can not be efficiently supplied by available laser systems. The need exists for a one-photon process which can efficiently utilize readily available photons, particularly infrared (IR) photons.